Chairs for dental professionals are increasingly designed to prevent back strain and injury. The bent forward position is required to work on the patient's mouth could cause significant back problems over the long term.
One known device for helping to reduce back strain is a chair arm that can pivot around its support post and lock into a desired position. The arm is shaped to allow the user to rest the front of their torso on the rest as they lean forward. This type of armrest is made by Mathison, Adec and Link Erogmomics. These arms rotate freely toward the body of the user, but can be locked in place to prevent rotation in the opposite direction, allowing the user to rest their body weight against the armrest when the user leans forward.
One known type of arm rest uses a single direction ratchet in the arm rest support to allow for rotation in one direction and locking the in the other direction. One limitation of such arms is that since the ratchet can only lock into positions determined by the “teeth” of the ratchet, the arm is not infinitely adjustable. Finer adjustments can be created by having a ratchet with smaller, closely spaced, teeth. However, the smaller the teeth, the more breakage of teeth over time become a problem.
The present invention solves this problem by allowing providing a pivoting support that freely rotates in one direction, and can be locked into position in any position in the other direction of rotation.
In other applications it is known the art to have rollers for feeding sheets of material (fabric, paper, plastic etc) through feeding rollers. The column of the present invention can also be used as a feed roller in applications where the material should feed in only one direction unless the user unlocks the roller, to clear a jam for example.